Using v26.x

KC_HOSTNAME is set to <hostname>:<kc-hostname-port>/auth

Realm A has realmsettings/frontendUrl: <hostname>:<kc-hostname-port>/auth
Realm B has realmsettings/frontendUrl: <hostname>:<realm-b-port>/auth

When a user in realm A logs in a redirect sends the browser to:
<hostname>:<kc-hostname-port>/auth/realms/<realm-name>/protocol/openid-connect/auth...

When a user in realm B logs in a redirect sends the browser to:
<hostname>:<realm-b-port>/auth/realms/<realm-name>/protocol/openid-connect/auth...

I need to move all realms to redirect to:
<hostname>:<realm-b-port>/auth/realms/<realm-name>/protocol/openid-connect/auth...

It seems that the kcadm.sh script is no longer able to set a realms frontendUrl attribute,

bin/kcadm.sh update realms/test-realm -s frontendUrl=<hostname>:<realm-b-port>/auth
null [Invalid json representation for RealmRepresentation. Unrecognized field "frontendUrl" at line 1 column 4251.]

is there a setting that will override that attribute for all realms

UPDATE
If I completely remove Realm B realmsettings/frontendUrl, then login it now redirects to
<hostname>:<kc-hostname-port>/auth/realms/<realm-name>/protocol/openid-connect/auth...